Computer network components that communicate using RF radiation, wires or IR radiation are well known. Dedicated ultrasonic acoustic links are known for various types of electronic devices. Typically, high frequencies are used, to increase bandwidth and reduce noise.
However, such dedicated communication mechanisms require that the computer network components have installed thereon specialized communication hardware. Installing such hardware on an existing computer may be expensive and/or problematic. Further, some electronic and/or computer embedded devices, for example cellular telephones may be “sealed” products, to which it is impossible to add internal components.
PCT publications WO96/10880, WO94/17498, WO93/21720 and WO93/11619, the disclosures of which are incorporated herein by reference describe an electronic device which transmits coded information to a microphone of a telephone using a DTMF-like encoding scheme. A WWW page addressed “http://www.encotone.com/html/tech_def.html”, available Feb. 1, 1999, but possibly published prior to that date, suggests using such a device to transmit audible DTMF-like tones to a personal computer using the computer's sound card.
Two way communications using audible DTMF-like tones, between a smart-card and a telephone communication system is described in U.S. Pat. No. 5,583,933, the disclosure of which is incorporated herein by reference.